A Method to Obtain a Good Infrared Spectrum of the Wet Acetone Gas Sample without Any Drying PretreatmentSCIEI北大核心CSCD

Water vapor in the beam of a Fourier transform infrared (FTIR) spectrometer or/and in a gas cell is a major source of interference in the infrared measurement of a gas sample. In general, in order to eliminate the effect of water vapor, we have to completely remove these molecules before the measurement of any spectrum. Herein, we provide an approach to collect an IR spectrum of a gas (wet acetone) sample free from water vapor interference without any drying pretreatment. After dozens of scans, the air atmosphere in the sample compartment of the FTIR spectrometer will be slightly adjusted by small amounts of dry air or wet air (room air) depending on the property of water vapor lines (absorbance> 0 or absorbance <0). Water vapor lines will then gradually disappear when the ensuing collection process is continued. The experiment results demonstrated that this method is a facile and very effective way to remove water vapor interference. Moreover, this method works still well for the measurement at 0.5 cm(-1) resolution, typically used in the gas infrared measurement.     

不需干燥预处理过程获得含水汽的丙酮气体样品的高质量红外光谱

测量气体样品的红外光谱时,红外光谱仪器内的水汽和气体样品中所含的水汽会严重干扰气体的红外光谱。为消除水汽的干扰,通常作法是测量前必须将水分子(气态)彻底排除掉,也就是使光谱仪器和气体样品保持干燥状态。该研究提供一个新测量方法,不需任何干燥预处理过程,直接获得含水汽的丙酮气体的红外光谱。经过几十次光谱扫描累加后,观察并根据水汽谱的吸收峰性质(吸光率>0或吸光率<0),向光谱仪样品室引入少量干燥氮气或少量潮湿空气,在接下来的光谱扫描累加过程中,水汽吸收峰将逐渐变小直至消失。实验结果表明该方法去除水汽干扰峰简单高效。新方法在0.5 cm-1光谱分辨率时效果非常好,为气体的高分辨分析提供了有力工具。     

Condensation-induced dynamic gas fluxes in a mixture of condensable and non-condensable gases

It is shown that condensation of water vapor produces dynamic instability of atmospheric air and induces air circulation that is characterized by observable air velocities and persists independently of the magnitude of horizontal temperature gradients.     

反常吸收与高质量的远红外光谱

在水汽含量恒定但相对湿度较大的情况下,远红外光谱仪得不到理想的100%线。这表明过高的水汽含量将会导致反常吸收现象。反常吸收的出现将严重影响远红外光谱的质量。研究了光谱仪内部空气相对湿度和光谱分辨率对反常吸收的影响,发现降低水汽含量和采用适当光谱分辨率可以有效抑制反常吸收现象,对获得高质量的远红外光谱很有益处。在无反常吸收现象发生的实验条件下,采用"湿度中和法"在空气湿度波动的情况下也可以得到理想的100%线,这为快速获得高质量的远红外光谱提供了新测量方法。     

Two-dimensional characterization of atmospheric profile retrievals from limb sounding observations

Limb sounders measure atmospheric radiation that is dependent on atmospheric temperature and constituents that have a radial and angular distribution in Earth-centered coordinates. In order to evaluate the sensitivity of a limb retrieval to radial and angular distributions of trace gas concentrations, we perform and characterize one-dimensional (vertical) and two-dimensional (radial and angular) atmospheric profile retrievals. Our simulated atmosphere for these retrievals is a distribution of carbon monoxide (CO), which represents a plume off the coast of south-east Asia. Both the one-dimensional (1D) and two-dimensional (2D) limb retrievals are characterized by evaluating their averaging kernels and error covariances on a radial and angular grid that spans the plume. We apply this 2D characterization of a limb retrieval to a comparison of the 2D retrieval with the 1D (vertical) retrieval. By characterizing a limb retrieval in two dimensions the location of the air mass where the retrievals are most sensitive can be determined. For this test case the retrievals are most sensitive to the CO concentrations about 2° latitude in front of the tangent point locations. We find the information content for the 2D retrieval is an order of magnitude larger and the degrees of freedom is about a factor of two larger than that of the 1D retrieval primarily because the 2D retrieval can estimate angular distributions of CO concentrations. This 2D characterization allows the radial and angular resolution as well as the degrees of freedom and information content to be computed for these limb retrievals. We also use the 2D averaging kernel to develop a strategy for validation of a limb retrieval with an in situ measurement.     

水汽分子对CO_2谱线加宽的影响

报道了以高分辨力连续可调谐中红外差频激光为探测光源,结合可调长光程怀特池,利用直接吸收的方法探测了CO2的10011←10002带R支以及部分P支在室温下的水汽加宽吸收光谱。在2422cm-1到2457cm-1范围内共有26条吸收谱线被探测到,采用Voigt线型对吸收谱线进行拟合,得到了CO2光谱的水汽加宽系数,结果显示CO2的水汽加宽系数平均比干燥空气的加宽系数大52%。利用实验测得的CO2的水汽加宽系数与HITRAN04数据库中CO2谱线的线位置、线强和干燥的空气加宽系数进行比较,分析了在实际大气中(海平面,10km光程)不存在水汽和存在水汽(含有2.0kPa水汽)时该波段CO2的大气透过率,结果表明潮湿空气与干燥空气之间的最大透过率差约为0.5‰。     

Numerical modelling of acoustic cavitation threshold in water with non-condensable bubble nuclei

Numerical modelling of acoustic cavitation threshold in water is presented taking into account non-condensable bubble nuclei, which are composed of water vapor and non-condensable air. The cavitation bubble growth and collapse dynamics are modeled by solving the Rayleigh-Plesset or Keller-Miksis equation, which is combined with the energy equations for both the bubble and liquid domains, and directly evaluating the phase-change rate from the liquid and bubble side temperature gradients. The present work focuses on elucidating acoustic cavitation in water with a wide range of cavitation thresholds (0.02–30 MPa) reported in the literature. Computations for different nucleus sizes and acoustic frequencies are performed to investigate their effects on bubble growth and cavitation threshold. The numerical predictions are observed to be comparable to the experimental data in the previous works and show that the cavitation threshold in water has a wide range depending on the bubble nucleus size.     

湿空气饱和水蒸汽曲线计算模型的建立与分析

湿空气物性的高精度计算中,饱和水蒸汽曲线的计算建模是关键所在。在对已有的饱和水蒸汽压力公式进行误差分析比较后,得到了Gerry方程误差最小的结论。为解决计算的连续性问题,重新界定了该方程中冰面及水面方程的分界点。其次,建立了两种高精度的t-p公式,可方便直接的计算湿空气露点温度。最后,分析了饱和蒸汽曲线斜率的意义,推导出它的计算式。以上建立的湿空气饱和水蒸汽曲线计算模型,不仅具有快速方便的物性计算功能,还提供了准确判定湿空气状态变化的准则。     

Luminescence and structure of ZnO-ZnS thin films prepared by oxidation of ZnS films in air and water vapor

Effect of water vapor quantity at oxidation of undoped ZnS films on structural and luminescent properties of the obtained films was investigated. The films were deposited onto glass substrates by electron beam evaporation. ZnO-ZnS layers were prepared by thermal oxidization of ZnS films at 600 °C in dry or wet atmospheres. The films were characterized by X-ray diffraction, atomic force microscopy and photoluminescence spectroscopy. As-deposited ZnS films were sphalerite crystal structure. The “dry annealing” led to the ZnS phase transition from sphalerite to wurtzite structure and from ZnS to ZnO for a small fraction of the film. After the “wet annealing” the amount of ZnO phase with wurtzite structure growing along the 〈0 0 0 2〉 direction varied from 25% to 95% in dependence on the water vapor quantity. Photoluminescent spectrum at room temperature exhibits green emission with maximum at 2.4 eV. A strong influence of the water vapor on shape and intensity of the emission was observed. Photoluminescent spectra at 22 K consisted of two bands—high-energy band at 2.1-2.4 eV and low energy band at 1.7-1.8 eV. Location and intensity ratio depended on the preparation conditions.     

基于灰色关联分析的BP神经网络对混流闭式冷却塔出水温度的预测

通过控制变量法对混流闭式冷却塔进行测试, 采用灰色关联分析法对影响出水温度的因素进行筛选, 将关联度较大的5个因子作为输入参数, 进而建立灰色_BP神经网络预测模型, 对混流闭式冷却塔的出水温度进行预测。操作参数包括进水温度、湿球温度、补水温度、循环水流量和风量, 输出值为出水温度。网络采用三层结构, 隐含层神经元数为4个, 迭代次数为30 000次, 使用不涉及训练阶段的实验数据来验证所建立的模型。结果表明, 灰色_BP神经网络模型比传统BP神经网络模型的预测结果更加准确, 其预测值与实际值的相关系数、平均相对误差、均方根误差, 分别为0.998 9、0.293 4%和0.152 9, 因而可认为灰色_BP神经网络是预测混流闭式冷却塔出水温度的有效工具。     

Movement of liquid gallium dispersing low concentration of temperature sensitive magnetic particles under magnetic field

In this work, a temperature sensitive functional fluid was synthesized, and then its movement under the influence of magnetic field was investigated. Silica coated FeNbVB particles, prepared by chemical synthesis, were dispersed into liquid gallium, because they have a relatively high magnetization and a high temperature dependency. The synthesized functional fluid (solid fraction of 0.3 mass%) showed temperature dependence for magnetization within the testing temperature range between 298 and 353 K. The movement of gallium based fluid under the influence of the magnetic field with a magnetic field gradient was observed at various temperatures. We found that at 318 K, fluid displacement of the synthesized functional fluid is better when compared with the fluid displacement at 348 K.     

Theory of inert gas-condensing vapor thermoacoustics: propagation equation

The theory of acoustic propagation in an inert gas-condensing vapor mixture contained in a cylindrical pore with wet walls and an imposed temperature gradient is developed. It is shown that the vapor diffusion effects in the mixture are analogous to the heat diffusion effects in the thermoacoustics of inert gases, and that these effects occur in parallel with the heat diffusion effects in the wet system. The vapor diffusion effects can be expressed in terms of the thermoviscous function F(lambda) used in the theory of sound propagation of constant cross-section tubes. As such, these results can be extended to any shape parallel-walled tube. The propagation equations predict that the temperature gradient required for onset of sound amplification in a wet-walled prime mover is much lower than the corresponding temperature gradient for an inert gas prime mover. The results of a measurement of the onset temperature of a simple demonstration prime mover in air with a dry stack and with a stack wetted with water provide a qualitative verification of the theory.     

Performance of a dehumidifying compression heat pump with auxiliary heat input

Experiments are carried out on a R114 dehumidifying heat pump installed in a closed circuit drying tunnel. The influence of auxiliary heat input before condenser and/or evaporator are studied. Actual coefficient of performance varied from about 2 to 3. Studies throw light on the significance of the location of the auxiliary heat input in the drying circuit. It is observed that the dryer temperature could be controlled within certain limits using the low grade heat input before the condenser or evaporator. This could substitute high temperature heat conventionally input after the condenser. This is also significant if the same dryer has to be used for drying different materials which require different drying temperatures.     

Accelerating flames in tubes—an analysis

Flame acceleration in tubes is studied. A tube filled with flammable mixture is closed at one end and open to the atmosphere at its second end. When ignition takes place near the closed end, it is well-known from experiments that the flame may accelerate, oscillate and eventually reach considerable speeds. A one-dimensional analysis is presented, based upon the assumption that the flame front propagates at a speed that is small compared to the speed of sound. The analysis leads to a construction of the complete unsteady solution. Results from the analysis and from a numerical simulation are compared. They are similar enough to validate the analysis. The tube acoustics are set in motion by the expansion of the fluid due to ignition at the closed end. Subsequently, both spectrum and amplitude evolve because of the motion of the temperature interface, and because of forcing by the flame front, which the analysis precisely quantifies. Oscillations in the front position are strong enough to result in flow reversal. In addition, the induced periodic acoustic acceleration of the temperature and density interface will periodically make the flame front Rayleigh–Taylor unstable, which should result in the dramatic increase in the propagation speed seen in experiments.     

Predictions of arc temperature profiles using approximate emission coefficients for radiation losses

Coefficients are calculated for the net emission of radiation per cc from the center of cylindrical isothermal plasmas of various temperatures and radii. Coefficients are given as a function of temperature and radius for the D lines of sodium vapor at 250 torr and for the continuum radiation of air at 1 and 30 atm. These coefficients are used in the Elenbaas Heller equation to derive temperature profiles of wall stabilized arcs e.g. for 4·5A with a radius of 0·35 cm in sodium vapor at 250 torr and 10,000 and 20,000A with a radius of 1 cm for air at 30 atm. Comparisons are made with calculated temperature profiles where self absorption effects and the radiation transfer are treated exactly, but still assuming thermodynamic equilibrium. It is found that the approximation using the net coefficients yields central arc temperatures and electric field strengths for a given arc current accurate to 10 per cent. Computation time for the approximate calculation is more than an order of magnitude less than for the calculation where radiation transfer is treated exactly. Thus the approximation facilitiates an account of line radiation for arc plasmas having complex spectra.     

Properties of metallocene complexes during the oxidative crosslinking of air drying coatings

Driers are added to air drying paints to accelerate the hardening of spread coating. For decades cobalt octoate has been the most widely used drier because of its good performance at ambient temperature. Recently, several reports describing possible carcinogenity and genotoxicity of cobalt and cobalt salts, such as cobalt sulfate in aerosols, have appeared. It is necessary to reduce the amount of cobalt compounds in coatings industry. Present study deals with the possibility of using ferrocene and its derivatives as driers for air drying coatings. We concentrated particularly on the synergic effect between these metallocene complexes and the cobalt drier. In the first step the kinetics of autooxidation by FTIR spectroscopy in model systems was investigated. Then the metallocene complexes were applied together with cobalt drier to alkyd resin, where their influence on hardness of spread coatings was examined.     

Drying processes in the presence of temperature gradients --Pore-scale modelling

The European Physical Journal E - The influence of temperature gradients on the drying of water-saturated porous networks has been studied. We have focussed on the influence of the temperature on...     

Dependence of the characteristics of bubbles on types of sonochemical reactors

Computer simulations of bubble oscillations in liquid water irradiated by an ultrasonic wave have revealed that the characteristic of bubbles depends on types of sonochemical reactors: a horn-type reactor and a standing-wave type reactor. When the acoustic amplitude is large at 20 kHz, the bubble content is mostly water vapor even at the end of the bubble collapse and the temperature inside a bubble at the collapse is relatively low. On the other hand, when the acoustic amplitude is relatively low, the bubble content is mostly noncondensable gas at the end of the bubble collapse and the bubble temperature is relatively high. In a horn-type sonochemical reactor, the former type of bubbles are dominant because many bubbles exist near the horn-tip where the acoustic amplitude is large, while in a standing-wave type reactor the latter type of bubbles are dominant because the Bjerknes force gathers bubbles at a region where acoustic amplitude is relatively low.     

Dy或Tb掺杂的MgB4O7磷光体的热释光特性

用高温固相反应法研制了MgB₄O₇:Dy和MgB₄O₇:Tb两种热释光材料.用自制的三维热释光谱仪测量了两种磷光体的三维发光谱,从MgB₄O₇:Dy磷光体的三维发光谱观察到:1.热释光发光峰峰温为220,380℃;2.Dy³⁺离子的发光波长为480,575,660nm;3.220,380℃发光峰的相对强度随高温固相反应温度的升高而变化,但发光峰温和波长基本保持不变.由MgB₄O₇:Tb磷光体的三维发光谱可看到在230,340,420℃附近有三个发光峰,发光谱线波长分别为489,543,589,620nm.不同的高温烧结温度不仅对发光峰的发光强度有很大影响,而且还对Tb³⁺发光谱形产生影响,当温度高于850℃时Tb³⁺离子发光谱线开始变成了发光谱带.此外,对比MgB₄O₇:Dy和MgB₄O₇:Tb两种热释光材料的二、三维发光谱,得出了掺入三价稀土离子的热释光材料的发光峰峰温主要由基质材料决定,发光波长则取决于稀土离子的4f电子能级间的跃迁.     

Application of ultrasound technology in the drying of food products

This study presents a state-of-the-art overview on the application of ultrasound technology in the drying of food products, including the ultrasound pre-treatment and ultrasound assisted drying. The effect of main parameters and ultrasound technology on the drying kinetics and food quality were discussed. Inconsistencies were pointed out and analyzed in detail. Results showed that for ultrasound pre-treatment, the food products may lose or gain water and increase of ultrasonic parameters (sonication time, amplitude and ultrasound power) promoted the water loss or water gain. When ultrasound technology was applied prior to drying, an increase in drying kinetics was always observed, though some different results were also presented. For ultrasound assisted drying, the ultrasound power always gave a positive effect on the drying process, however, the magnitude of ultrasound improvement was largely dependent on the process variables, such as air velocity, air temperature, microwave power and vacuum pressure, etc. The application of ultrasound technology will somehow affect the food quality, including the physical and chemical ones. Generally, the ultrasound application can decrease the water activity, improve the product color and reduce the nutrient loss.